Heretofore, as vehicle seat reclining apparatuses of this kind, there has been known one which is described in Patent Document 1, for example. The apparatus described in Patent Document 1 is provided with a lower arm held on a seat cushion and having a plurality of pawls each with an outer gear at one end and an upper arm rotatably supported by the lower arm with itself secured on a seatback and formed with an inner gear being able to mesh with the outer gears of the pawls. Then, by changing the meshing positions of the inner gear with the outer gears, it is possible to adjust the inclination angle of the seatback.
In the seat reclining apparatus described in Patent Document 1, in order to simultaneously move the plurality of pawls radially of a rotation shaft for the lower arm and the upper arm, there is provided a locking mechanism having a cam which is arranged rotatably relative to the lower arm. In the seat reclining apparatus like this, in order to make a passenger easy in getting on and off with respect to a rear seat by rotating the seatback forward relative to the seat cushion, there is provided a so-called “forward folding mechanism” which is capable of bringing the outer gears of the pawls out of meshing with the inner gear of the upper arm in an angular range beyond a predetermined angle so that the seatback can be rotated through a large angle. This mechanism is constructed so that the respective pawls are provided with protrusions while the upper arm is formed with respective contact portions at positions facing the protrusions of the respective pawls in a forward folding angular range, to obstruct meshing engagements between the outer gears of the pawls and the inner gear of the upper arm.